The present invention relates to a supporting apparatus for a magnetic head which is in contact with a magnetic layer of a photographic film, on which a transparent magnetic layer is coated, and at least, records information or plays back the recorded information.
Recently, the performance of respective apparatus consisting of a photographic system, for example, film, camera, processing apparatus, etc. has been greatly improved. However, because information interchange between apparatus is not satisfactory, it is difficult to further increase the performance of apparatus and decrease costs of the total system. For example, a current color printing system presumes photographic conditions from a optical density of a developed negative image, determines printing conditions, and performs printing so that the printing will satisfy the greatest number of customers. Accordingly, the printing is carried out so as to obtain a print having an average characteristic, thereby photographic conditions and the photographer's intentions can not fully be reflected on the print, and the performance of a film and camera can not be fully exhibited. Accordingly, in order to fully respond to user's requirements, it is necessary to carry out printing including the photographic conditions. Further, since the post-exposure treatment of the film is carried out in darkness or in water, transmission of the information is difficult, so that computerized automation is difficult.
As a means for easily interchanging information in a photographic system, the following systems have been proposed in International Applications WO-90/04205, WO-90/04214, U.S. Pat. Nos. 4,975,732, 4,975,732, etc.: a system in which a substantially transparent magnetic recording layer is provided over the entire back surface of the film, and required information is directly recorded on that magnetic layer of the film. That is, at the time of film production, the manufacturer's name, the type of the film, the emulsion lot, sensitivity, manufacturing date, any reference signals, etc., are recorded. At the time of exposure, photographing conditions, for example, the color temperature of the light source, brightness of the subject, the exposure time, the F-number, rear-lighting or not, using flash or not, continuous photographing or not, the type of a camera, the owner's ID, the date of exposure, the photographer's memoranda, etc., are recorded for each frame of the film. Further, when a DPE shop receives the exposed film, customer order information, for example, sizes of prints, the number of prints, the finished condition of prints (silk finish, or gloss finish), etc. are recorded in the film. At the time of printing, this information is read out from the film, and printing conditions are determined from the information accompanied with optical density data obtained when the negative film is scanned. By the above-described operations, prints which reflect the photographic conditions and the photographic intention can be obtained. Further, these printing exposure conditions are recorded in each frame of the film, and when the recorded information are read out at the time of reordering prints, prints having the same color tone as the first print can be obtained. As described above, since the photographic information can be directly magnetically recorded on each frame of the film, photographic processing can be automatically computer controlled, resulting in decrease of cost, increase of quality, rapidity of processing, improved service control, etc. Features of this system are as follows: the film can perfectly correspond to the information when the information is directly recorded on the film; and the information can be easily interchanged between apparatus even when the film conveyance speed is not determined between apparatus when a signal modulation system, which is insensitive to chage and fluctuations of the film conveyance speed, is adopted into this system.
As a recording means for recording the information other than the image on a film, a recording means except the magnetic recording means, for example, an electrical, or optical means can be considered. However, these means have the following disadvantages: the electrical means using an IC memory, etc., are expensive; and the optical means using LEDs, etc., has a small memory capacity, and is not rewritable. Accordingly, a means by which information is directly magnetically recorded on the film, is most suitable for this purpose as a means in which the cost is low, the recording density is high, the information memory is freely rewritable, the image perfectly corresponds to the information, and the information can be easily interchanged between apparatus.
Generally, magnetic recording is carried out as follows: a signal current flows in coils of a magnetic head (hereinafter, called a head); and a magnetic layer is magnetized by a generated magnetic field for recording. Reproducing is carried out when the head coil picks up the leakage flux from the surface of the magnetic layer. Since the leakage flux, generated from a head-gap or the magnetic layer surface, is very small, and the attainable distance of the leakage flux is very short, a reproducing output and the S/N ratio are greatly lowered when the head is not in correct contact with the magnetic layer and a small gap exists between the head and the magnetic layer. When a portion of signals is missing, serious errors occur. Accordingly, the surface contact, of the surface of a medium, with the head surface is very important. In magnetic recording, a track is provided on a recording medium and signals are recorded on the track. Tracking is regarded as important because a reproducing output or an S/N ratio is greatly lowered when the head can not correctly trace the track. Further, in magnetic recording, because the medium is magnetized by the leakage flux of a magnetic head-gap, and the leakage flux of the medium is picked up by the reproducing head-gap, it is necessary that the angle of the recording head-gap is equal to that of the reproducing head-gap. Even when the difference between two angles is only 1 degree, the reproducing output is greatly lowered. This phenomenon is referred to as an azimuth loss, and it is important to prevent it. Generally, a magnetic recording medium is made in such a manner that the magnetic material is densely packed. The reason for this is that the reproducing output or the S/N ratio depends on the packed amount of magnetic material. Further, in magnetic recording, the running speed and position of the recording medium are strictly specified, and are essential requirements in magnetic recording. In contrast to the foregoing, the method, by which a film is directly magnetically recorded, according to the present invention, is largely different from the conventional magnetic recording method. For example, in a photographic processing apparatus, when a 3-part recording modulation system, etc. is adopted which has been disclosed in U.S. Pat. Nos. 4,912,467, 4,876,697, and 5,025,328, it is not necessary that the running speed is strictly controlled in the same way as that in conventional magnetic recording apparatus. Further, in order to maintain the film transparency, the amount of the magnetic material used for the magnetic layer provided on the film is limited to 1/50 to 1/100 of the amount used for normal magnetic recording medium. Accordingly, the reproducing signal intensity obtained from the film is extremely small. In a normal magnetic recording medium such as a video tape which is made in the manner that a large amount of magnetic material is packed, its influence is small even when some degree of head contact failure, tracking error, or azimuth loss is caused, because its reproducing output is high. However, the output of the transparent magnetic layer is 1/50 through 1/100 of that of a normal magnetic recording medium. Therefore, signals tend to be missed when head contact failure, tracking error, or azimuth loss is caused, and there is also the possibility that serious errors are caused. As described above, in recording on and reproducing from the transparent magnetic layer, it is important to prevent head contact failure, tracking error, or azimuth loss. However, since the film is stiffer than the magnetic tape, and curl or core-set is larger, head contact failure, tracking error, or azimuth loss occurs easily. Further, since the running accuracy of the photographic processing apparatus is greatly reduced from that of the magnetic recording apparatus, tracking error or azimuth loss easily occurs. As described above, recording on and reproducing from the transparent magnetic layer of film include more difficult technological problems than those of conventional magnetic tapes.
Conventional magnetic recording is compared with magnetic recording in a film with a substantially transparent magnetic layer in the present invention, and problems at the time of recording on and reproducing from the magnetic layer provided on the film will be described below. Here, the transparent magnetic layer is very thin (not more than 1 .mu.m, preferably 0.1 .mu.m), and the ratio of the magnetic layer on the film is small. Accordingly, physical properties of the film with the magnetic layer are regarded as substantially the same as those of the photographic film, in this explanation.
Generally, a magnetic tape consists of a thin support base and a specifically soft binder such as polyurethane in order to obtain the correct contact of the head with the tape.
In contrast to this, the thickness of the support of the film is 5 to 10 times that of the tape. Since photographic emulsion is dissolved in water and dispersed, and it is subjected to water system coating, binder to be used is limited to water soluble resin which is hard and which has poor flexibility. Therefore, the film is much stiffer than the tape, and is not flexible. Since several ten-layers of foundation layer, photosensitive layer, protective layer, etc. are formed on the support base of the film, the film is very complex compared with the magnetic tape. An anti-curl layer is provided on the opposite side of the film support. However, if the balance between layers is lost, the film tends to curl extremely. Further, if silver is removed during development, the physical properties of the film may change. Specifically, the stiffness or curling condition may change greatly. Further, since the film is processed in wet and dry processes, curling occurs dependent on the degree of drying. The degree of drying is easily changed depending on fluctuations of temperature and humidity. Not only does extreme curling occur over the width direction of the film, but also extreme core-set occurs along the length of the film. These factors are complex in the film, and non-uniform strain occurs in the film.
The transparent magnetic layer is coated over the entire surface of the film, and information can be recorded on the entire surface. However, since recording density is high in magnetic recording, the edge portions outside the image area can be sufficient for recording such information. Generally, photographic film is stiffer than magnetic tape, and often curls concavely in such a manner that the emulsion surface is inside the curl of the film. Especially, extreme curling occurs at the edge portions. Further, this curled portion fluctuates greatly depending on a lapse of time, temperature and humidity variance, developing processing, and other factors. Accordingly, it is difficult to obtain good head contact in the edge portion at which the strong curling occurs.
So-called magnetic film, in which a magnetic layer is provided on the same support base as the photographic film, is used for audio recording on movies. This magnetic film is also stiff and head contact property is poor. However, since the amount of magnetic particles used is not limited, magnetic layer, the amount of which is several times of that of normal magnetic tapes, is used so that an excellent S/N ratio can be obtained. Accordingly, its output is high and head contact property is less problem. Further, in audio recording, an instantaneous signal skips are not so serious. However, in recording in the photographic film, digital codes are used, so that as a general rule signal skips are not acceptable.
As described above, magnetic recording on film with a transparent magnetic layer includes far more difficult problems compared with conventional magnetic recording. The present invention can solve these problems by a new magnetic head supporting apparatus.
A head supporting apparatus for photographic film has been disclosed in U.S. Pat. Nos. 5,034,836, and 5,041,933. These apparatus are structured as follows: both edges of the film are sandwiched with two film guides on which heads are attached; the entire head unit makes an arc motion depending on the fluctuation of the film angle; and a large number of bearings are combined so that the heads can follow the irregularity of the film edges. These inventions cope with track deviation of the head caused by irregularities of the film edges.
Further, an invention has been disclosed in U.S. Pat No. 5,005,031, in which the head is tilted 3 to 4 degrees in such a manner that the head conforms to the curl of the film, in order to approximate the head to the degree of tilt of the film caused by the curl. In this invention, good head contact can be obtained. However, since the curl of the film varies greatly depending on changes of temperature or humidity, even when the head is tilted in such a manner that the head conforms to a predetermined curl, excellent head contact can not always be realized. Further, because the shape of a head portion is not regulated, there is the possibility that the film can be damaged.